Hypervalent iodine in synthesis. Part 54: One-step conversion of aryl aldehydes to aroyl azides using a combined reagent of (diacetoxyiodo)benzene with sodium azide

Article abstract of DOI:10.1016/S0040-4039(00)00990-4

Aroyl azides are readily prepared from the corresponding aryl aldehydes with the aid of (diacetoxyiodo)benzene (DIB) and sodium azide in high yields. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4039(00)00990-4

Tetrahedron Letters 41 (2000) 7361±7363
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Hypervalent iodine in synthesis. Part 54: One-step conversion
of aryl aldehydes to aroyl azides using a combined reagent of
(diacetoxyiodo)benzene with sodium azide
Da-Jun Chen and Zhen-Chu Chen*
Department of Chemistry, Zhejiang University at Xixi Campus, Hangzhou, 310028, China
Received 16 March 2000; revised 26 April 2000; accepted 14 June 2000
Abstract
Aroyl azides are readily prepared from the corresponding aryl aldehydes with the aid of (diacetoxy-
iodo)benzene (DIB) and sodium azide in high yields. # 2000 Elsevier Science Ltd. All rights reserved.
The versatile synthetic utility of hypervalent iodine reagents is of current interest. When the
combined reagent of iodosylbenzene or [bis(acyloxy)iodo]benzene with trimethylsilyl azide or
sodium azide is employed, an azido function is introduced to the substrate through a radical
1
mechanism. Typical examples include the azidonation of ole®ns to a-azidoketones and vincinal
diazides,1 b-dicarbonyl compounds to a-azido-b-dicarbonyl compounds, 2-(trimethylsilyoxy)-
,2
3
4
5
furan to 5-azido-2(5H)-furanone, silyl enol ethers to b-azido silyl enol ethers, and p-alkylanisoles
to arylalkyl azides. These encouraging results, coupled with the susceptibility to homolytic rupture
of aldehydic C±H bonds, prompted us to examine the possibility of achieving direct oxidative
azidonation of aldehydes to acyl azides using this methodology.
6
7
Our method is limited to the synthesis of thermally stable and isolable aroyl azides (Scheme 1),
which are of substantial utility as precursors of isocyanates leading to other amine derivatives.8
Simple stirring of a mixture of an aryl aldehyde, DIB and NaN in CH Cl under a N
3
2
2
2
atmosphere at room temperature gave, after work-up and isolation, the desired aroyl azide free of
Scheme 1.
*
Corresponding author.
Zhang, P. F.; Chen, Z. C. Hypervalent iodine in synthesis. Part 53: Synthesis of 2,4-disubstituted and 2,4,5-tri-
substituted 1,3-selenazoles. Synthesis, in press.
y
0040-4039/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)00990-4

7
362
1
Curtius rearrangement product. The products were characterized by H NMR, IR and m.p.
which were consistent with literature data.9
,10
The e€ect of substituents was observed by comparing the results with a strongly electron
donating aryl group (entry 2, Table 1) and an electron withdrawing one (entry 8). The reaction is
applicable to a variety of aryl substituents.
Table 1
Synthesis of aroyl azides (ArCON
3
)11
As depicted in Scheme 2, the mechanism of this conversion may involve [bis(azido)iodo]-
benzene, which is formed by ligand exchange followed by homolytic decomposition to generate
6
an azido radical. The starting aldehyde is azidonated via a usual H-abstraction and coupling
process.
Scheme 2.
Even though numerous procedures for the preparation of aroyl azides are available,1
majority involve the conversion of carboxylic acids to acid chlorides or anhydrides, which are
2�26
the
then reacted with azide reagents.1
2�18
In view of this, investigations in this ®eld have been mainly
concerned with the starting carbonyl compounds.2
1�26
Herein, we provide a facile and ecient
synthetic route to aroyl azides starting from aryl aldehydes. Having advantage over recent
methods such as ease of manipulation, mild conditions and accessible starting materials, our
approach serves as a practical alternative for the synthesis of aroyl azides.

7
363
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